The ECR (Electron Cyclotron Resonance) plasma source can generate a highly dense plasma uniformly in a plasma generating chamber so that it is used as a plasma source for a semiconductor laser, an SAW (Surface Acoustic Wave) device, or a device for sputtering or etching an LSI.
The ECR plasma source comprises a plasma generating chamber, a magnetic coil and a microwave introducing portion. The ECR sputtering or etching device of the prior art has been intended mainly for a wafer-shaped circular sample placed still. Therefore, the ECR plasma source for those device comprises: a plasma generating chamber having a circular sectional shape in a plane normal to a plasma flow; a magnetic coil wound to have a circular sectional shape in a plane normal to the plasma flow; and a microwave introducing portion having a structure for introducing the microwaves either directly or in a branching and binding method from a microwave waveguide (as referred to Japanese Patent Application Publication No. 01-036693 (1989) (Japanese Patent No. 1553959 or “Deposition of High Quality Thin Films Using ECR Plasma” by Amazawa et al., Reports of Precision Engineering Society Vol. 66, No. 4, 511 (2000).
Especially in the case of the sputtering device, the branching and binding method is frequently utilized so as to prevent target particles from contaminating a microwave introducing aperture (usually made of a quartz plate).
FIG. 5A and FIG. 5B are diagrams for explaining an example of the construction of an etching device, which comprises the ECR plasma source of the prior art having a circular section. FIG. 5A is a top plan view, and FIG. 5B is a sectional view taken along VB-VB′ from FIG. 5A.
In the etching device comprising the ECR plasma source of the prior art having the construction shown in FIG. 5A and FIG. 5B, the plasma generated in a plasma generating chamber 70 flows through a plasma drawing opening 14 and irradiates a sample 100 arranged in a sample chamber 11. In this case, the plasma generated in the plasma generating chamber 70 establishes a downward plasma flow directed from the plasma generating chamber 70 to the sample 100, as shown in FIG. 5B.
Considering the shape of the sample 100 to be treated, the plasma generating chamber 70 is shaped to have a circular sectional shape in a plane normal to that plasma flow. On the other hand, magnetic coils 80 and 81 are wound in a circular shape in a plane normal to the plasma flow, and are designed to establish a magnetic field for the ECR conditions at a predetermined position in the plasma generating chamber 70. Microwaves are introduced into the plasma generating chamber 70 from a microwave guide 90 through a microwave introducing aperture 91 (usually utilizing a quartz aperture) so that electrons in the magnetic field are efficiently accelerated by the vibrating electric field of the microwaves.
In the so-called “FPD (Flat Panel Display) device” such as a liquid crystal display, a plasma display or an organic EL (Electro Liminescence) display, the development of which has been progressed, the sputtering or etching treatment is demanded for a large-sized sample of about 50 cm×60 cm.
In order that this treatment may be coped with the ECR plasma source of the prior art in which the plasma generating chamber has the circular section in the plane normal to the plasma flow, however, the ECR plasma source has to be diametrically enlarged. In this case, there arise problems: (1) the plasma generating chamber and the magnetic coil are enlarged to make the ECR plasma source extremely expensive; and (2) in the ECR plasma source having the circular section, it is difficult to sputter or etch the large-sized generally rectangular FPD sample uniformly.